1. Field of the Invention
The present invention relates to a plug and connector clamp for maintaining engagement between an electrical plug and connector, and more specifically, to such a clamp for accomplishing this without forcibly gripping the electrical cords.
2. The Prior Art
A portable electrical appliance such as a power saw, vacuum cleaner or the like is often used with an extension cord connected to the electrical cord of the appliance. The connected cords sometimes snag on obstructions during movement of the appliance and pull apart the connection between the plug of the appliance and the female fitting or connector of the extension cord. Sometimes the plug and connector only partially separate, dangerously exposing portions of the plug contacts.
Various contrivances have been proposed for clamping together such a plug and connector to prevent their inadvertent separation. These include the devices described in U.S. Pat. Nos. 2,753,536 (Tjader); 3,609,638 (Darrey); 3,999, 828 (Howell); and 4,221,449 (Shugart, Jr.), none of which satisfactorily prevents electrical fittings from being pulled apart.
The device disclosed by Howell employs a friction clamp to frictionally grip the cord of a fitting, to retain the fitting in mating contact with a second fitting. However, such a friction clamp does not work reliably when the cord is wet or oily. Moreover, if such a clamp is used repeatedly on the same cord, the cord insulation is eventually damaged by the abrading action of the clamp.
The device disclosed by Darrey is adjustable only after removal from the cords being clamped. Further, it is characterized by protrusions that can snag on foreign objects, especially if the joined cords are dragged over rough ground.
The Shugart device is retained in position by the engagement under tension of a locking member having serrations. The Tjader device employs a spring clamp. Both devices are subject to abrupt disengagement if subjected to vibration or a sudden pull on the cords.
It will be apparent from the foregoing that there is a need for a clamp adapted to reliably maintain engagement between an electrical plug and connector without damaging the plug and connector cords, and without protusions or the like which are likely to snag on foregin objects.